McTester allows you to write fully automated integration tests against Minecraft. Through an easy-to-use API, you can direct a real singleplayer client to perform actions in the world (esnding commands, looking around, clicking the mouse). Combined with a server-side API like Sponge, McTester allows you to write automated tests that simply wouldn't be possible otherwise. Without McTester, the only way to perform these kinds of tests is by manually running the game. With McTester, you can run tens or hundreds of tests as part of your normal build process. You no longer have to decide when to test that a difficult-to-reproduce bug hasn't re-emerged.